Clearer error when a job hits a full disk (ENOSPC) (#1899)

[arimu1]

Problem

Fixes #1899.

When the user's temporary drive (or output directory) fills up while a job is running, the underlying OSError carries errno 28 (ENOSPC, "No space left on device"). In JobBase._execute this fell through to the catch-all branch:

else:
    _logger.exception("Exception while running job: %s", str(e), ...)
processStatus = "permanentFail"

…which dumps a stack trace and gives the user no hint that the actual problem is a full disk (the symptom reported on the CWL forum thread linked from the issue: a tool silently produces empty outputs).

Fix

Add a dedicated ENOSPC branch to the existing OSError handler in cwltool/job.py, right next to the ENOENT ("command not found") case that's already special-cased there. It logs a concise, actionable message instead of a traceback:

[job foo] No space left on device. The temporary directory (/tmp/…) and/or
output directory (/…/out) may be full; free up space, or point --tmpdir-prefix
and --outdir at a location with more capacity.

The full traceback is still available with --debug (the branch passes exc_info=runtimeContext.debug, matching the sibling cases). I also changed the existing magic-number e.errno == 2 to the named errno.ENOSPC's counterpart errno.ENOENT for readability, now that errno is imported.

Tests

tests/test_examples.py::test_disk_full_error_message injects an OSError(errno.ENOSPC, …) at the job's output-handling stage (monkeypatching cwltool.job.bytes2str_in_dicts) during a normal echo run, and asserts:

• the message contains "No space left on device" and the --tmpdir-prefix guidance,
• no raw Traceback (most recent call last) is printed,
• exit code is 1 (permanentFail).

I verified this test fails against the unpatched code (it hits the old generic-exception/traceback path), proving it guards the behavior. black, flake8, and isort are clean on the changed files.

This addresses the "provide a better error message" ask in #1899. Actually probing free space ahead of time is a larger, platform-specific change and isn't attempted here.

---

This change was produced with the assistance of Claude Code (model: Claude Opus). The diff, root-cause analysis, and test were reviewed by a human before submission.

[mr-c]

@arimu1 thanks for using cwltool and contributing your fixes. Let's get the existing PRs resolved before opening more.

Perhaps you can fix the codecov upload issue. Maybe the version needa bumping? If that doesn't work, I would accept a temporary disabling of CodeCov, but then reviews will take longer as I will have to personally check the code coverage locally.

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 77.47%. Comparing base (5634342) to head (323ea61).

Files with missing lines	Patch %	Lines
cwltool/job.py	75.00%	0 Missing and 1 partial ⚠️

❗ There is a different number of reports uploaded between BASE (5634342) and HEAD (323ea61). Click for more details.

HEAD has 6 uploads less than BASE

Flag	BASE (5634342)	HEAD (323ea61)
	17	11

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2293      +/-   ##
==========================================
- Coverage   85.18%   77.47%   -7.71%     
==========================================
  Files          46       46              
  Lines        8593     8596       +3     
  Branches     2011     2012       +1     
==========================================
- Hits         7320     6660     -660     
- Misses        807     1409     +602     
- Partials      466      527      +61     

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